The present invention relates to the use of organic light emitting diodes for area illumination.
Solid-state lighting devices made of light emitting diodes are increasingly useful for applications requiring robustness and long-life. For example, solid-state LEDs are found today in automotive applications. These devices are typically formed by combining multiple, small LED devices providing a point light source into a single module together with glass lenses suitably designed to control the light as is desired for a particular application (see, for example WO99/57945, published Nov. 11, 1999). These multiple devices are expensive and complex to manufacture and integrate into single area illumination devices. Moreover, LED devices provide point sources of light that are not preferred for area illumination.
Conventional illumination devices such as incandescent or fluorescent light bulbs are bulky, fragile, and problematic to handle and ship. Although the bulbs are filled with gas, the glass tubes are easily broken and occupy substantial space, especially in comparison to the actual light emitting area or material of the device. The bulbs must be carefully packed and require a large volume for shipping.
Existing solid-state lighting elements may be planar and hence easy and cost-effective to ship but do not address the need for lighting elements that have a variety of conventional three-dimensional shapes as found, for example, in light bulbs for decorative lighting. It is also useful if a lighting device is readily and safely replaced by consumers at minimal cost.
There is a need therefore for an improved, replaceable OLED area illumination device having a simple construction using a single substrate, is compatible with the existing lighting infrastructure, is efficient to ship, and provides a variety of three-dimensional shapes.
The need is met by providing lighting apparatus that includes a solid-state area illumination light source, having: a planar flexible substrate, a flexible organic light emitting diode (OLED) layer deposited on the flexible substrate, the organic light emitting diode layer including first and second electrodes for providing electrical power to the OLED layer, a flexible encapsulating cover covering the OLED layer, and first and second conductors electrically connected to the first and second electrodes, and extending beyond the encapsulating cover for making electrical contact to the first and second electrodes by an external power source, whereby the light source may be stored in a space saving planar configuration; and a lighting fixture for removably receiving and holding the light source in a curved 3 dimensional configuration, the lighting fixture including a support for holding the light source in the curved configuration and contacts for providing electrical contact between said first and second conductors and an external power source.
The present invention has the advantage of providing a lighting apparatus having a light source that can be stored efficiently in a planar configuration, thereby saving considerable storage space. Another advantage is that the planar flexible light sources are not fragile and can be packaged in thin, unpadded packaging.